Superbroad bandwidth cathode-ray tube device



June 13, 1967 HARUO MAEDA 3,325,663

SUPERBROAD BANDWIDTH CATHODERAY TUBE DEVICE Filed May 28, 1964 #44 fia 02w ATTORNEYS United States Patent 3,325,663 SUPERBROAD BANDWIDTH CATHODE-RAY TUBE DEVICE Haruo Maeda, Tokyo, Japan, assignor to Matsushita Elec- Itric Industrial Co., Ltd., Osaka, Japan, a corporation of apan Filed May 28, 1964, Ser. No. 370,776 Claims priority, application Japan, May 31, 1963, 38/28,400 7 Claims. (Cl. 313-30) ABSTRACT OF THE DISCLOSURE An electron beam deflecting system of the travelingwave type having a periodically folded structure with the system being held in a superconductive state. The electron beam is directed parallel to the axis of the structure to periodically traverse the transverse electric field of a signal propagating through the circuit.

The present invention relates to superbroad bandwidth cathode-ray tube devices. l

For observation and measurement of super high speed pulses or so-called millimicrosecond pulses, traveling-wave oscilloscopes have been suitably employed which include in their signal deflecting system a traveling-wave type delay line having a uniform electron-beam deflection sen sitivity characteristic over an extremely wide frequency range. At present, however, this type of oscilloscope has a band of operating frequencies the upper limit of which is defined by the signal transmission characteristic of the slow-Wave circuit including a helix or folded circuit as a deflecting system. In fact it has been difiicult to impart any uniform transmission characteristic to the slow-wave circuit in a frequency band including as more than 2000 or 3000 megacycles per second. More over, such conventional slow-wave deflecting systems involve a serious attenuation adversely aifecting the phase characteristic of the signal particularly in a very high frequency range. With such systems, therefore, it has been difficult to transmit super high speed pulses without any distortion, which necessitates an extremely wide frequency bandwidth. To overcome the above difliculties and enable accurate observation of waveforms with high sensitivity, it is necessary to minimize the attenuation of the deflecting circuit over a frequency band required for such observation while maintaining the linear phase characteristic.

From this point of view, the present invention proposes to employan electron beam deflecting system of the traveling-wave type in the form of a coaxial slow-wave circuit including a helical or other periodically flexed structure and hold such system in a superconductive state.

According to the present invention, there is provided a superbroad bandwidth cathode ray tube device which is free from the above deficiencies of conventional deflecting systems deriving from their attenuation and phase characteristics and thus exhibits a high and uniform sensitivity over an extremely wide frequency bandwidth of several scores of thousands of megacycles.

The phenomenon of superconductivity has already been fundamentally investigated and accounted for with a variety of metals. Also, it is well known that a coaxial cable including a core conductor of metal niobium, an external conductor of lead and an insulation of Teflon, if cooled down with liquid helium to assume .a superconductive state, forms a practically ideal transmission line which has practically no attenuation effect over a wide frequency range of from DC. to a vicinity of the point of mode change while maintaining the linear phase characteristic peculiar to coaxial cables. The frequency range, normally frequencies as high depending upon the cross-sectional dimensions of thc coaxial cable, extends from tens of kilomegacycles tr about kilomegacycles for smaller cables.

According to the present invention, a traveling-wave cathode-ray tube includes such superconductive coaxial tube bent into helical or other folded form and usable as a slow-wave circuit for its geometrical structure and a narrow electron beam is directed along the axis of the slow-Wave circuit in such a manner as to periodically run across the transverse electric field of the signal propagating through the circuit. With this arrangement, it is obvious that the velocity of the electron beam must be matched with the phase velocity relative to the axis of the slowwave circuit, which includes a coaxial cable bent into a geometrical formation.

The foregoing and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic cross-sectional view of a cathode-ray tube device embodying the present invention;

FIG. 2A is a longitudinal cross-sectional view of the coaxial type slow-wave deflecting system in the device shown in FIG. 1; and

FIG. 2B is a transverse cross-sectional view of the same.

Referring to the drawings, and particularly to FIG. 1, which illustrates the entire structure of the device in cross-section, reference numeral 1 indicates an electron gun for forming a beam of electrons 2 and reference numeral 3 indicates .a coaxial deflecting circuit held in a superconductive state. The electron beam 2 is directed through a portion of the space defined between the core and external conductors of the coaxial cable and meanwhile is deflected by the transverse electric field of the signal propagating through the coaxial tube. Coaxial lines 4 and 5 are connected to the input and output sides of the coaxial deflecting circuit 3 for leading in and out the signal. The coaxial deflecting circuit 3 is entirely fitted in a cryostat and held in a superconductive state therein. The cryostat is comprised of a metal mass 6 for heat conduction, a chamber 7 formed therein for holding liquid helium, and containers 10 and 11 for liquid nitrogen arranged to heat-shield said metal block and liquid helium chamber. Additionally, an outer casing 12 is provided to enclose these components and hold them in vacuum. In this embodiment, the casing is formed with an opening 13 through which it is evacuated by a vacuum pump, not shown. The liquid nitrogen container 11 has apertures 111 and 112 formed in its opposite side walls for the purpose described below. On the remote side of casing 12 from theelectron gun I are arranged a horizontal deflecting system 8 and a fluorescent screen 9 similar to one used in ordinary cathode-ray tubes. In operation, the electron beam emitted from the electron gun I proceeds through one of said apertures 111, formed in the adjacent wall of the heat-shielding liquid nitrogen container 11, through the restricted space defined between the core and external conductors of the superconductive coaxial deflecting circuit 3, and through the other aperture 112, formed in the opposite side wall of the container 11, and further passes through the horizontal defleeting system 8 to reach the fluorescent screen 9. The screen 9 may be substituted by a target for cumulatively recording the signal in the form of a beam trace.

Description will next be made on the details of coaxial deflecting circuit 3 with reference to FIGS. 2A and 2B.

The deflecting coaxial circuit includes an external conductor of rectangular cross section and a core conductor in the form of a fiat strip 15 and practically is constructed as follows. The heat-conducting metal block 6 shown in FIG. 1 actually includes three sections 61, 62 and 63 arranged concentrically in spaced relation with each other. A helical partition or flange 17 is formed about the periphery of the central section 61 and the core conductor of the coaxial line takes the form of a strip wound helically between the adjacent turns of the helical partition 17. The intermediate section 62 encircles the helical partition 17 to define a helical space between the adjacent turns thereof. That portion of the helical space which lies between the central section 61 and the helical strip or core conductor is filled with an insulating material 16 and the remaining portion of the helical space, which lies between the core 15 and the intermediate section 62 is left open as at 14. The turns of the partition 17 are each apertured as at 18 to define a narrow passageway which extends in a direction axial of the concentric assembly and through which the electron beam 2 can proceed. The annular chamber 7 between the intermediate and outer sections 62 and 63 serves as a container for liquid helium. To summarize, the deflecting coaxial line of such helical construction has a heat-conducting metal block on both inside and outside thereof and is continuously held in a superconductive state.

It has been found that, by employing as a travelingwave type deflecting circuit a coaxial line of the helical or other periodically folded structure and maintaining its superconductive state, as described above, an operating bandwith can be readily obtained which is at least ten times as broad as that obtainable with conventional noncooled deflecting systems including a helical or folded wire structure. Also, the electric field of the signal, acting upon the electron beam, has a definite phase velocity over an extremely broad bandwidth including low frequencies and higher frequencies over tens of thousands of megacycles and the line has no attenuation effect. This enables the signal to proceed through the line from its input to output end while maintaining its original waveform. In other words, the length of the deflecting system can be extended as required to enhance the deflection sensitivity of the device as a cathode ray tube. In case the electron transit time through the deflecting gap defined in each stage of coaxial line becomes more than negligible compared with the length of one period in a range of higher operation frequencies, be reduced due to the transit time effect. To prevent this, the dimensions of the coaxial line should be selected under due consideration of the electron velocity or the beam voltage.

Having described one embodiment of the present invention including a fabricated vacuum device, it is to be understood that various changes and modifications can be made without departing from the spirit and scope of the invention as defined in the appended claims. For example, the inventive device can take the form of a sealed-off type cathode-ray tube having a deflecting coaxial line inserted in or connected to a cryostat by way of a transmitting metal.

What is claimed is:

1. A superbroad bandwidth cathode ray tube device comprising a traveling wave-type electron-beam deflecting circuit serving as a slow-wave circuit, said circuit includ- 60 ing a periodically flexed structure, means for holding said deflecting circuit in a superconductive state comprising a the deflection sensitivity may 7 cryostat surrounding said deflecting circuit and heat shielding means surrounding said cryostat, an electron gun for forming a beam of electrons, a target for said electron beam, said deflecting circuit lying between said gun and said target substantially parallel with said electron beam whereby said electron beam is directed along the axis of said deflecting circuit so as to periodically traverse the transverse electric field of a signal propagating through said circuit.

2. A superbroad bandwidth cathode ray tube device according to claim 1, wherein said periodically flexed structure is a helix.

3. A superbroad bandwidth cathode ray tube device comprising a closed casing, a target fixedly mounted in one side of said casing, an electron gun fixedly mounted in an opposite side of said casing for directing a narrow electron beam at said target, a deflecting circuit substantially parallel with said electron beam and including input and output lines connecting a core conductor to a signal source, .a cryostat enclosing said deflecting circuit, said cryostat comprising a metal mass for heat conduction, said metal mass having a chamber therein for passing coolant fluid about said deflection circuit, and coolant fluid filled container means mounted between said casing and said cryostat serving as heat shielding means for the latter.

' 4. A superbroad bandwidth cathode ray tube device according to claim 3 wherein said heat conducting metal mass comprises three concentrically mounted spaced members, the central member having a helical flange formed about the periphery thereof, said core conductor being in the form of a strip wound between turns of said helical flange, the intermediate member enclosing said helical flange thereby defining a closed helical space, insulating material partially filling said helical space, a portion of each turn of said flange having an aperture therein defining a narrow passageway for said electron beam, the router member and said intermediate member defining therebetween a chamber for the passage therethrough of coolant fluids.

5. A superbroad bandwidth cathode ray tube device according to claim 3 wherein means are provided for evacuating said casing.

6. A superbroad bandwidth cathode ray tube device according to claim 3 wherein horizontal deflecting means are provided between said deflecting circuit and said target.

7. A superbroad bandwidth cathode ray tube device according to claim 3 wherein said deflecting circuit is helical.

References Cited UNITED STATES PATENTS 2,800,605 7/ 1957 Marchese 315--3.5 2,914,736 11/1959 Young 332-5l 2,972,697 2/ 1961 Johnson et al 313-431 3,005,128 10/1961 Goldberg et al. 315-18 3,118,110 1/ 1964 Spangenberg 324-77 3,280,361 10/ 1966 Goldberg et al. 3 l5-3 JAMES W. LAWRENCE, Primary Examiner. V. LAFRANCHI, Assistant Examiner. 

1. A SUPERBROAD BANDWIDTH CATHODE RAY TUBE DEVICE COMPRISING A TRAVELING WAVE-TYPE ELECTRON-BEAM DEFLECTING CIRCUIT SERVING AS A SLOW-WAVE CIRCUIT, SAID CIRCUIT INCLUDING A PERIODICALLY FLEXED STRUCTURE, MEANS FOR HOLDING SAID DEFLECTING CIRCUIT IN A SUPERCONDUCTIVE STATE COMPRISING A CRYOSTAT SURROUNDING SAID DEFLECTING CIRCUIT AND HEAT SHIELDING MEANS SURROUNDING SAID CRYOSTAT, AN ELECTRON GUN FOR FORMING A BEAM OF ELECTRONS, A TARGET FOR SAID ELECTRON BEAM, SAID DEFLECTING CIRCUIT LYING BETWEEN SAID GUN AND 